Distillation of tar and recovery of products therefrom



Feb. 9, 1932. P, LLER 1,844,892

DISTILLATION 0F TAR AND RECOVERY OF PRODUCTS THEREFROM Filed April 20.1927 2 Sheets-Sheet l I .Deca/z fer Q INVENTOR BY i lo ATTORNEYS Feb. 9,1932. I 5, p R 1,844,892

DI' STILLATION OF TAR AND RECOVERY OF PRODUCTS THEREE ROM Filed April20. 1927 E Shee tS-Sheet 2 C5412 One/:1

INVENTOR ATTORNEYS Patented Feb. 9, 1932 UNITED STATES PATENT OFFICESTUART IPARMELEE MILLER, OF TENAFLY, NEW JERSEY, ASSIGNOB 1'0 J3EEBARREL! COMPANY, OF NEW YORK, N. Y A CORPORATION OF NEW JERSEY DISTILLATIOIN F TAB AND RECOVERY OF PRODUCTS THEBEFBDI Application filed April20, 1927. Serial llo. 185,185.

This invention, relates to improvements in the distillation of tars andoils, particularly to the utilization of the heat available in the gasesproduced in coal carbonization plants 5 to distill coal gascondensates,'and to the production of oils and tars containing onlyasmall percentage of insoluble impurities. The invention will bedescribed especially with reference to its application to coke ovens.-

In the ordinary operation of by-product coke-ovens, the gases producedby the coking operation pass from the individual ovens through uptakepipes and goose-necks to a collector main common to the ovens of thebattery. The gases commonly known as foul gases leave the ovens at hightemperature, e. g., 600 to 700 C. or higher and carry a considerableproportion of volatilized and entrained tars and oils as well as solidparticles of coke, coal and carbon and other impurities. Ordinarily, thegases are cooled as rapidly as possible by the application of sprays ofammonia liquor or ammonia liquor and tar in the goose-necks andcollector main, the heat in the gases being thereby dissipated and lost.The rapid cooling causesseparation of tar containing heavier oils in thecollector main.- Further cooling is efiected in the cross-over mainwhich connects the collector main to the condensing system. An

additional quantity of tar carrying both heavier and lighter oils isrecovered in the cross-over main and in the condenser. The collected taris ordinarily shipped from the coke-oven plant to a tar distillationplant for distillation and separation of the oils and the production ofpitches of varying qualities. Handling losses, freight charges anddistillation costs, including fuel and capital and maintenance expensesfor the special equipment required for distillation add to the cost ofproduction of the tar distillation products.

It is the object of the present invention to a coke-oven plant or othercoal carbonization plant, the utilization of the heat of the cokeovengases for that purpose, and par'ticularl the production of salable oilsdirectly by suc distillation together with pitches havmg'the provide amethod for thedistillation of tar at.

- ovens are collected as tar and contain considerable amounts of dust,coke braize and free carbon. It is one of the purposes of this inventionto treat the hot coke oven gases in such a manner as to'allow the subseuent direct recovery of salable distillate oil ractions and salablepitch, thus avoiding the necessity for distillation of tar as ordinarilycarried out.

On cooling coke oven gases, according to the ordinary methods, a fog ormist of tar particles is produced. Due to the extremely small size ofthese particles, the tar fog persists in large quantities in the gaseseven after cooling to atmospheric temperatures. Hence, oily fractionsrecovered by stepwise cooling of the gases have been so contaminatedwith tar that the fractions have not been salable as oils but have beenutilized as tars. It has been necessary to distill them for productionof salable oils. The residue from the distillation has been pitch.

According to this invention, salable oils may be recovered directly fromthe gas stream. The heat of the gases from a coal carbonization processis utilized in volatizing tar or oil, the volatile portions of which arerecovered as marketable products at a subsequent step of the process. Byenrichin the gases in condensable constituents whic are subsequentlyrecovered as salable products, the percent of entrained tar fog andsolid impurities in the gases, using the condensable constituents as abasis for figuring the percentage, is less than the percent of entrainedtar fog and solid impurities in the same gases not thus enriched withcondensable constituents, using the condensable constituentsin the gasas a basis for figuring the percentage.

The process of this invention comprises two operations. The firstoperation involves enriching the gases with condensable constituents.and the second operation comprises scrubbing the enriched gases.Scrubbing removes entrained tar and solid impurities to a substantialdegree. Both operations combine to reduce the percentage of impuritiesin the products and make possible the recovcry of marketable productswith a low percentage of insoluble impurities direct from the gasstream.

According tothe present invention, the coke oven gases while at hightemperature are utilized to distill tar or oils brought directly incontact with them. The gases are greatly enriched in condensableconstituents and are simultaneously somewhat cooled. The gases, whilestill at high temperature, are then passed through any one of a numberof suitable scrubbing devices in which they are brought into intimatecontact with tar or oil. In the first operation, i. e.,'the distillationoperation, a portion of the tar fog normally present in the gases isthrown down with the tar or oil brought in contact with the gases and isremoved as the residue from the distillation. Further tar tog is removedin the second or scrubbing operation.

The material used in the distillation operation may be a tar, a pitch oran oil. These materials may be those recovered from the coke ovens, orthey may be materials from another or other sources. Likewise, in thesecond or scrubbing operation tar, oil or pitch from thecoke ovens maybe used, or materials fronr another or other sources may be employed.The amount of distillation, and hence the extent of the cooling of thegases, may be regulated by controlling the amount, temperature of andcharacter of the tar, pitch or oil distilled. Likewise, the character ofthe residue from the distillation and the degree and character of gasenrichment will vary with amount, temperature of, and character of tar,pitch or oil distilled. In thescrubbing 0 eration, the gases may bescrubbed wit 1 tar, pitch or oil. Depending upon the character of thescrubbing material, its temperature and its amount, the gases will be(1) cooled, (2) held at the same temperature, or (3) heated; the de reeand character of enrichment will be decreased, held constant orincreased. In some cases, the degree of enrichment may be held constantbut the character of the enriching medium may be entirely altered as inthe case in which the hot gases are scrubbed with a low boiling oil. Insuch a. case, high boiling constituents in the gases will beprecipitated and will be replaced by lower boiling products, the extentof this replacement being determined by the regulation imposed on thesystem.

The gases leaving the second process, i. e, the scrubbing, will uponstepwise cooling yield fractions so low in tar or tree carbon that theyare salable as oils, rather than as tars. According to the preferredform of the present invention, the scrubbing is effected by a scrubbingdevice located in the hottest part of the crossover main near collectormain. At thi' point the gases are the exit from the hot and by thescrubbing solid matter and entrained tar can be removed withoutcondensing any considerable amount of the heavy oils and tars. Byregulating the temperature of the gases at this point and by regulationof the temperature of the spray of the scrubber, the quality of the taror pitch recovered from the scrubber may be regulated. If the gases arevery hot and a hot spray is used, a heavy pitch is recovered and heavyconstituents of the gases from which free carbon, etc. have been removedare thrown forward into the coolers where heavy constituents, as well aslighter constituents, are recovered in a readily marketable condition.

The temperature of the gases may be regulated by regulating the sprayingto which the gases are subjected prior to their entrance into thecrossover main. According to the usual practice, the gases are sprayedwith water or ammonia liquor in the collector main. Because of the highlatent and specific heats of water and ammonia liquor, it is desirablefor the purposes of this invention to spray with tar or tarconstituents-in the collector main instead of the usual aqueoussolution, inasmuch as by this procedure the temperature of the gases isnot lowered to the same extent as would result from spraying with thesame quantity of an aqueous solution. Likewise, the vapors are enrichedby volatilization of the volatile contents in the tar or oil sprayedinto the collector main. By decreasing the amount of tar or oil sprayedinto the collector main, or by preheating the spray, the temperature ofthe gases entering the cross-over main may be raised above the usualtemperature. By this procedure the quantity of heavy constituentscondensed in the collector main is kept at a minimum. Condensation ofthe constituents can likewise be retarded by diluting the vapors withsome inert gas.

The heat of the gases leaving the coke oven is sutlicient to distill aquantity of tar or oil many times that produced by the oven itself. Inthis invention, these additional tars or oil may be volatilized by beingadded to the system as fluids'with which to flush the collector main.They may be added to the main in excess of the quantity required toflush the main and if desired, recirculated through the main until thelighter constituents have been volatilized. They may be introduced intothe gases through spray nozzles. By preheating these fluids, thecapacity otthe system for recovering pure distillates is increased.

In order that the heat of the gases passing through the collectormain'may be utilized to the greatest extent, the materials to bedistilled should be brought into intimate contact with the gases.

It may be advisable to provide some means for agitating thenon-volatilized constituents which flow through the main. This may beaccomplished by providing a rotating shaft running thelen h of the main'on which are paddles or 'sks or other spray devices. Agitating means ascone sprayers may be inserted through the top of the collector main.Suction Ts (McDaniel type ejectors) may be located in the main withtheir suction ends beneath the level of the tar or pitch therein. When agas under pressure is supplied to such devices, the tar or pitch or oilin the main will be thrown into the stream of gasesin the main anddistillation of these products will be accomplished. 4

When it is desired to utilize the features of this invention to theutmost, the heatof the coke oven gases will be-used most efiiciently toproduce the maximum of enrichment of the gases that can be obtained. Inorder to accomplish this, the heat of the coke oven gases is utilized tothe fullest extent by treating the gases with volatile oils or tars,

instead of by cooling the gases with water or ammonia liquor as is thecustomary practice.

The scrubbing medium in the second step of the invention may be made toserve a double purpose. It serves 'to remove entrained tar and solidparticles from the gas.

' In addition to this, by volatilization of the light constituents ofthe scrubbing medium the gas may be further enriched, and a heavier tar,oil, or pitch may be produced at the scrubber. The volatilizedconstituents may subsequently be recovered as salable materials bycooling of the enriched gases.

Depending upon the quality of the oil, tar and pitch which it is desiredto recover, the nature of the recoverable constituents added to theprocess may be varied. Where several batteries of coke ovens areoperated in one plant, it is possible to equip one battery with meanssuch as is described in this application and to supply to this onebattery the tars and pitches or a portion of the tars and pitchesobtained in the operation of the other batteries; or it is possible toequip only a portion of the ovens of one battery with a separatecollector .main which leads to a separate cross-over main, in which atar scrubber is rovided, and byequipping only a portion c the ovens ofthe battery in this way utilize the oils, tars and pitches, or adesirable fraction of the oils, tars and pitches produced in theremainder of the battery in the operation oi the few ovens equipped withthe separate collector main and scrubber.

By adding only the-lighter fractions of tar and oils recovered from theoperation of other ovens to the gases from ovens equipped with thescrubber, a greater portion of light oils will he recovered, and,conversely, by adding a preponderance oi heavier fractions a greaterquantity of oils and tars or pitches of high boiling point will berecovered. In-

stead of coke oven by-products, tar such as gasthouse tar, verticalretort tar, or water gas tar, etc., or tars or oils from other sourcescan be distilled, and when blended or composite pitches or distillatesare desired, several difi'erent kinds of tars, oils or pitches may beadmixed in suitable proportions, and oil, tar or pitch of the desiredcomposition may be obtained directly. For example, horizontal gas retorttar high in free carbon will yield a composite-pitch higher in freecarbon than the pitch from coke oven tar together with a marketablecomposite distillate.

The tar, oil or pitch used in the collector main or scrubber may bepreheated in any suitable manner to reduce it to a thinly fluid stateand thus facilitate spraying into the hot coke oven gases and increasethe capacity of the gases for distillation.

It is possible to utilize the invention for the distillation ofcontaminated oils to recover therefrom clean salable products.

The enriched gases are washed in the scrubber and this may beaccomplished at a period in the recovery process when the heavier oilsare still in the vapor phase. It is generally advantageous to keep thetar in the scrubber at a temperature above the dew point of the gas forthe oil which it is desired to recover subsequently in the condensersystem.- If cool tar, or tar lower in temperature than the gas stream,is used, low boiling as well as high boiling constituents may be throwndown into the scrubbing medium, the gases may be impoverished incondensable constituents and smaller quantities of salable products willbe'su bsequently recoveredthan will be the case when a scrubbing mediumof higher temperature is used.

By controlling the temperature of the gases and the temperature andamount oi the tar supplied. to the scrubber and the temperature andamount of the constituents added in the collector main, the amount andthe character of salable oils subsequently recovered, as well as thenature'oi the. product produced at the scrubber, can be varied.

The enriched and somewhat cleaned gases produced by this process may becondensed in any desirable manner. It is a feature of this inventionthat by operating with the collector main hot and using a hot tarscrubber salable heavy'distillates may be recovered. Hitherto, therecovery of such salable heavydistillates irectly has not beenacc0mplished.

Although the invention has beendescribed in connection with a coke ovensystem and a the drawings are confined to coke oven operation,'it istobe understood that features of this invention are applicable to otheroperations in which gases containing entrained tar fog,dust or freecarbon are produced, and it is intended and will he understood that Fig.2 is an elevation, partly in cross-1 section, through the shortcollector main, of the plant shown in Fig. 1; and

Fig. 3 isa cross-section of the collector main showing one form ofagitating means.

The drawings show a battery of ovens 5,

four of which are connected. throughthe usual uptake pipes 6 with ashort collector main 7 having center box 8 and drain pipe 9 to a tarreceptacle 13. The tar from the receptacle 13 may be recirculatedthrough the short collector main by pump 20 which re' turns the tareither through the pipe 21 into the end of the collector main or throughthe pipe 22 through the sprays 14 and 15. The ammonia liquor may bedecanted through the outlet 23 before recirculatiomif desired. Tar fromthe balance of the ovens not connected with the short collector main maybe deliveredto thisshortcollection main through the pipe 24, or tar froman outside source may be delivered through the pipe 26. Each of theselines is equipped with a pre heater 25, so that the tar maybe preheatedif desired.

The gases from the short collector main enter the bottom of thescrubbing tower 30 situated in the hottest part of the cross-over mainand pass up through the tower countercurrent to the tar or oil which isdelivered through the sprays 31. The sprays may be fed through pipe 32from the tar storage 13, or they may be fed from an outside sourcethrough pipe 34. A preheater 33 is provided for preheating the tar whichis sprayed into the scrubber.

In the scrubber solid particles and entrained fog are removed andcollected together with the non-volatilized fraction of the spray at thebottom of the scrubber and delivered through the pipe 35 to the storage36. The purified gases pass from the scrubber through the pipe 37 to thecondenser38. Although an ordinary direct cooled condenser such ascommonly used at coke ovens is here shown, any satisfactory type ofcondensing means may be used. The condensed distillate is removedthrough the pipe 39 and de livered to the decanter40.

The greater part of the battery which is not connected with the shortcollector main sprays 51. The tar recovered in the collector main isdrawn off through the pipe 52 to the decanter 53. The tar is drawn oilinto a collector 54 and from there may be supplied to the scrubberthrough the pipe 55 or the tar from the decanter may be used to flushthe short collector main 7, in which case it is delivered through thepipe 24.

I Fig. 3 is a cross-section of the collector main 7 showing a shaft 61to which are attached paddles for agitating the tar in the collector'main to thereby aid in the volatilization of the light constituents ofthe tar. According to the preferred method of operation, tar from thedecanter 54 is conducted to the short collector main 7 in which it isbrought into intimate contact with the hot gases passlector main if aheavier product is desired in which case some of the heavy product iscontinually drawn otf from'the receptacle 13 to suitable storage. Thescrubber 30 is supplied from the decanter 54 through the line 55 or taror oil of a different character is supplied to the scrubber dependingupon the quality of the product which it is desired to recover from thescrubber. If a large quantity'of tar is supplied to the scrubber and itis desiredto further distill the light constituents-from this material,it may be recirculated to the scrubber through the line 60 by means ofthe pump 61 or may be allowed to overflow through the pipe 62 to thereceptacle 13, from which it may be pumped to I highest boiling productswill normally be recovered from the collector main and the cir' culationof tar or oil will be through the scrubber and thence to thecollectordnain. if the same material is to be treated in both thescrubber and the collector main, although in special cases it ispossible to use the product recovered in the collector main in thescrubber by removing it from the tank 13 by the pump63 and spraying itinto the scrubber.

Instead of withdrawing the tar from the center box of the long collectormain through the line 52 and conveying it thence to the scrubber andcollector main, the tarry oil recovered in the decanter 64, which isdrawn oii the condensers (35, may be conveyed to the short collectormain through the line 66 or to the scrubber through the line 67.

The volatilizcd constituents, together with the gases from the Coltsoven, pass up through the scrubber 30 where entrained solid par-- ticlesand tar fog are removed to a considerable degree. The vapors containingonly a small fraction of entrained tar fog and solid particles arewithdrawn from thescrubber and pass through the line 37 to the condenser38, and thence through the line all by means of the exhauster 42 to theusual apparatus for recovery of ammonia and light oils.

When it is desired to accurately control the boiling point of theconstituents contained in the gases coming oil of the scrubber throughthe line 37, this may be done by recirculating any suitable scrubbingmedium from the container 36 through thescrubber by means of the pump68. By controlling the temperature of the scrubbing medium by means ofthe heat interchanger 33, which may be either a preheater or a cooler asthe circumstances demand, and by regulating the composition of thescrubbing medium, for example, by adjusting the valve 70, which controlsthe outflow from the tank 36, and admixing with the scrubbing medium thenecessary quantity of low-boiling constituents which may be supplied byany suitable tar or oil recovered in the coke oven operation, orsupplied from an outside source 69, the scrubber 30 will operate tocondense higher boiling constituents than it is desired should be thrownover into the condensers. The lower boiling constitu-' ents suppliedthrough the sprays will be volatilized so that by controlling thetemperature, character and amount of the scrubbing medium, substantiallyall constituents with a boiling. point above that desired in theproducts recovered in the condenser will be condensed in the scrubberand drawn 03 through the line 35, and the excess heat of the gasesentering the scrubher will be absorbed as latent heat in the low boilingconstituents contained in the scrubbing medium which are volatilized. Bycontrolling the temperature and composition of the scrubbing medium inthis manner, not only will the nature of the gases passing ofi throughthe line 3'. be controlled, but it is also possible at the same time tocontrol the properties of the product withdrawn from' the bottom ot' thescrubbing device.

Variations of the process and apparatus here disclosed are possiblewithin the scope of this invention. The invention depends primarily uponthe distillation of tar by means or hot coke oven gases, for example, inthe collector main, and scrubbing oi the resuiting gases containing thevolatilized oils to remove solid articles and entrained tar mist. Thescrub ing is accomplished while the gases are still hot. in this waydistillates, both light and heavy, which are relatively free from dust,free carbon and other insoluble material, are obtainable in a directmanner. Although the features of this in ventien have been described inconnectien with a coke oven, it is to be understood that the inventionis of broader application as set forth in the attached claims.

In the claims, insoluble, as applied to the insoluble matter in tar oroil, is used with the meaning well-known in the art, viz. insoluble inavolatile bitumen solvent, such as benzol, carbon bisulfide, etc.

1. The method of distilling tar or pitch, which comprises bringing thematerial to be distilled into intimate contact with hot fresh coke ovengases while at a suliiciently high .temperature to bring about effectivedistillation thereof and produce pitch, subsequently scrubbing the gaseswith the pitch while still at a high temperature to give clean gasescontaining oil vapors from which relatively clean oils can besubsequently condensed and to give a pitch residue from the scrubbingoperation.

2. The method of distilling tar, which comprises collecting tar from thegases from the greater part of a coke oven battery in which coal isbeing coked by cooling the gases evolved therein, subjecting this tar todistillation by bringing it into direct contact with coal distillationgases from the ovens of another part of the plant, thereby distillingthe tar, and scrubbing the gases and,

vapors resulting from the tar distillation and cooling the resultinggases and vapors. to produce relatively clean oils and pitch.

3. The method of distilling tar, which comprises collecting coaldistillation gases from a plurality of the ovens or retorts of a coaldistillation plant in which coal is being distilled, bringing the tarinto intimate contact,

gaseswhile at a substantially high temperature to bring about efi'ectivedistillation, to:

produce pitch and to enrich the gases in oil vapors without substantialgasilication, scrubbing the gases with coal tar or pitch while they arestill at a highteinperature to remove entrained impurities and thencooling the scrubbed gases so as to condense distillate oil therefrom,together with oils originally present in vapor iorni in the coaldistillation gases.

5. The method of distilling. tar in hot coa. distillation gasesirons acoke oven battery in the ovens of which coal is destructively dis-=tilled which comprises conveying distillation gases ovens of the plantto a common gas collector main while still at a high teinperature,flushing the collector main with a,

quantity of coal tar sufiicient to prevent the accumulation of pitch inthe mainyspraying the tar into the gases in the collector main so as todistill the tar and produce itch Without substantial gasification of t etar, removing from the main gases and vapors resulting from thedistillation of the tar and scrubbing them with tar or pitch while theyare still at a, high temperature to separate suspended particles fromthem.

In testimony whereof I afiix my signature.

STUART PARMELEE MILLER.

